Cold start issue

[Janacek]

I think I've found my starting issue, the timing had slipped. I got it running a couple of days ago and ventured out with it but found that the performance was very flat and lacked the crispness that it should have and it dawned on me that the ignition was too retarded. On checking I found that fully advanced it was sparking almost at TDC, no wonder it wouldn't start. Although I'd previously set the ignition carefully I obviously couldn't have had the mag pinion fully seated on it's taper and it had moved. Doh!
I haven't yet reset it and I've now got a cracked soldered joint the oil feed pipe spigot to mend as well. Hopefully all will be fixed after the weekend.

I have had the ignition timing slip.
I lapped the mag cog onto the shaft with grinding paste,and a dab of Nutlock on the threads.So far so good!

[limeyrob]

A thought regarding timing slipping.  The magdyno has a slipping clutch for the dynamo drive. This is designed to reduce the mag dyno inertia and strain on the drive gear if the engine kicks back.  If its got stuck or stiff the usual failure is a row of stripped teeth on the fibre gear but it could also be enough to slip the gear on the shaft. Are you using the original fibre/steel gear or an after market ally one?

[Derek996]

I think I've found my starting issue, the timing had slipped. I got it running a couple of days ago and ventured out with it but found that the performance was very flat and lacked the crispness that it should have and it dawned on me that the ignition was too retarded. On checking I found that fully advanced it was sparking almost at TDC, no wonder it wouldn't start. Although I'd previously set the ignition carefully I obviously couldn't have had the mag pinion fully seated on it's taper and it had moved. Doh!
I haven't yet reset it and I've now got a cracked soldered joint the oil feed pipe spigot to mend as well. Hopefully all will be fixed after the weekend.

I have had the ignition timing slip.
I lapped the mag cog onto the shaft with grinding paste,and a dab of Nutlock on the threads.So far so good!

I think that in my case I too need to lap the mag pinion to the magneto shaft. It's a different armature and I don't think the fit is so good.

[limeyrob]

I use a needle file to take off any high spots and run a die down the thread so the nut runs smoothly and can be nipped up without the armature shifting.

[Derek996]

I use a needle file to take off any high spots and run a die down the thread so the nut runs smoothly and can be nipped up without the armature shifting.

What's the thread on the armature? It looks fairly coarse.

[limeyrob]

I think its BSF or Whit, I have a "garage" set of both so I see what fits.

[Derek996]

I think its BSF or Whit, I have a "garage" set of both so I see what fits.

I just checked the Lucas magnetos parts list which says 1/4" BSF